Phosphate esters of hindered phenols

ABSTRACT

Reaction products of a phosphate ester-forming compound such as a phosphorous oxyhalide and a hindered bis phenol are obtained. Such products are useful as antioxidants in various compositions and materials.

United States Patent [191 Robin et al. May 21, 1974 PHOSPHATE ESTERS OF HINDERED PHENOLS [56] References Cited [75] Inventors: Michael Robin, Colonia, N.J.; UNITED STATES P TE TS Sheldon R. Schulte, Columbus, Ohio 3,510,507 5/1970 Bown et a1 260/953 X [73] Assigneez Ashland Oil, Inc., Ashland, Ky. Primary Examiner Amon H. Sutto [22] Filed: May 15, 1972 21 App]. No.: 252,983 [57] ABSTRACT Reaction products of a phosphate ester-forming compound such as a phosphorous oxyhalide and a hin- [52] g g gg gg gg g g' dered bis phenol are obtained. Such products are use- 260/944 b 26O/947 260/949 26O/95 ful as antioxidants in arious compositions and materi- 51 Int. Cl. C07f 9/12, 801 1/18 [58] Field of Search.., 260/953, 936 5 Claims, N0 Drawings PHOSPHATE ESTERS OF HINDERED PHENOLS BACKGROUND OF THE INVENTION This invention relates to novel phosphate esters. More particularly it relates to reaction products of phosphate ester-forming phosphorous compounds and hindered bis phenols.

Synthetic polymers such as polyethylene, rubber, waxes, oils, fats and numerous other compounds are attacked by oxygen and eventually may become useless uous chain reaction until stopped. In order to prevent such degradation, various antioxidants have. been added to the polymers to react with and destroy the intermediate chemical free radicals as they form, without producing-equally reactive intermediates.

Various phosphorous-containing compounds and various phenols such as 2,2'-methylenebis(6-tertbutyl-4-methylphenol) have been used as antioxidants; however, the prior antioxidants have-the disadvantage of losing effectiveness at comparatively high temperatures, even when used in synergistic combinations. Continuing work is therefore being done to obtain compounds with improved antioxidant properties, We

have found that the novel compounds of our invention surprisingly and unexpectedly exhibit increased stabilizing properties; and thereby the quantity necessary to achieve a desired level of stabilization at such temperatures as are normally used for molding, calendaring, extrusion and other forming processes is reduced. Moreover, with the novel compounds of our invention, substantial degrees of stabilization can be attained at those higher temperatures at which combinations of phosphorous compounds separate and his phenolic compounds are ineffective.

BRIEF DESCRIPTION OF THE INVENTION The novel compounds of this invention are phosphate esters in'which at least one of the available bonds on the phosphorous atom is connected to a parasubs tituted hindered phenol through the oxygen remaining after the removal of the hydrogen of a phenolic hydroxyl group. The para-substituted hindered phenol is a hindered bisphenol with the two phenolic rings bridged through a saturated aliphatic hydrocarbon linkage, and with at least one hydroxyl group on each ring being ortho or para to the saturated aliphatic hydrocarbon linkage, and with both of the positions ortho to the OH group on each ring being substituted with bulky hydrocarbon groups of at least one carbon atom.

The term para-substituted hindered means that all positions ortho and para to the OH group on-each ring of the hindered bisphenol are substituted. All available bonds on the phosphorous atom, from which the bonds to the double bonded phosphate oxygen atom are ex- 2 cluded, are. connected to a hindered phenolic com pound through the oxygen remaining after removal of the hydrogen of the phenolic hydroxy group. The novel compounds of our invention may constitute, for instance, the reaction products of about one reacted mole of a phosphate ester-forming phosphorous compound and at least one reacted mole and preferably three reacted moles of a para-substituted hindered phenol, and if necessary at least one other hin dered phenolic compound in an amount so that each of the available bonds on the phosphorous atom is connected to a hindered phenol through the oxygen remaining after the removal of the hydrogen of a phenolic hydroxyl group. The para-substituted hindered phenol is a hindered bisphenol with the phenolic rings bridged through a saturated aliphatic hydrocarbon linkage, and with at least one hydroxyl group on each ring being ortho or para to the linkage, and with both ofthe positions ortho to said at least one hydroxyl group on each ring substituted with a bulky hydrocarbon group of at least one carbon atom. The term parasubstituted hindered means that all positions ortho and para to the OH group on each ring of the phenol are substituted.

The reaction products are formed under known phosphate ester-fonning conditions of time and temperature with known catalysts.

The production of the novel compounds or reaction products of the invention was unexpected since it was generally believed heretofore among those of ordinary skill in the art that the hydroxyl groups in fully hindered phenols such as are used herein, are virtually unreactive and cannot be converted to various derivatives by hindered phenols is discussed in, Kirk and Othmer, En-

, cyclopedia of Chemical Technology, Vol. '1, pages 902 and 906. Indeed it is quite surprising and unexpected that the hindered phenols used herein react with the phosphorous compounds under normal phosphate ester-forming conditions.

DESCRIPTION OF PREFERRED EMBODIMENTS The phosphorous compounds used-in preparing the compounds of the invention can be any of the known phosphate ester-forming compounds. Examples of such compounds are phosphoric acid, phosphorous oxyhalides, and phosphorous pentahalides such as thechloride. The preferred phosphorous compounds are the phosphorous oxyhalides such as phosphorous oxychloride, phosphorous oxybromide, and phosphorous oxyiodide. The most preferred phosphorous compound is phosphorous oxychloride.

The para-substituted hindered phenol compounds are represented by the following formula:

I. R'n

R is a saturated aliphatic hydrocarbon linkageor group (alkylidenes and alkylenes) having 1-8 carbon atoms, and preferably having l-4 carbons atoms. More preferably, R can be methylene, ethylene, isopropy- 3 4 lene, ethylidene, n-propylidene, and isopropylidene. methylenebis-(4,6-di-tert.-butylphenol); 2,2- The most preferred R group is methylene. methylenebis-(4,6-dimethylphenol); 2,2-

The OH group on each ring is either ortho or para to isopropylidenebis-(4,6-di-tert.-butylphenol); 2,2- the hydrocarbon linkage and is most preferably in the methylenebis-(6-nonyl-4-methylphenol); 2,2- ortho position. ethylidenebis-(4,6-di-tert.-butylphenol); and 4,4-

Each R individually is a bulky hydrocarbon group of methylenebis-(2,6-di-tert.-butylphenol). The preferred at least one carbon atom and is ortho to the OH group para-substituted hindered phenol is 2,2-methylenebison each ring. Usually the bulky hydrocarbon group is (4-methyl-6-tert.-butylphenol). free of nonbenzenoid unsaturation. R is preferably a The other hindered phenol is a mono or polyphenolic bulky hydrocarbon group of from 1-22 carbon atoms 10 compound which may be either a hydroxy substituted such as methyl, ethyl, t-butyl, t-amyl, t-hexyl, cyclophenol, or a phenol with at least two of the positions hexyl, t-pentyl, t-octyl, phenyl, naphthyl, amethylcyortho and para to the hydroxyl group on each phenolic clohexyl, nonyl, benzyl, methyl, isobornyl, anthranyl, ring being substituted with the appropriate ortho andphenantranyl, norbornyl, cyclopropyl, cyclopentyl, /or para substituents as defined above for the parabicyclohexyl, cyclobutyl, 1,2-dimethylcyclopropyl, and substituted hindered phenol. xylyl, more preferably R is a bulky hydrocarbon of Suitable examples of the hydroxy substituted phenol from 1-12 carbon atoms, and even more preferably is are catechol, resorcinol, and hydroquinone. Suitable an alkyl group containing 1-12 carbon atoms of which examples of a phenol with at least two of the positions t-butyl is the most preferred. ortho and para to the hydroxyl group on each phenolic ring being substituted are 2-tert.butyl-4-methylphenol, n 1 or 2-tert.butyl-4-chlorophenol, 2,6-dimethylphenol, 2,6-

R is any substituent which will occupy the position di-tert.-butyl-4-methylphenol, 4,4-bis-(2,6-di-tert.- para to the OH group on each ring, when it is unfilled, butylphenol), 2,4,6-trimethylphenol, and 2-methyl-4- in order to prevent the reactants from combining n-butylphenol. through said para position. R" advantageously is but is Thecatalyst used in preparing the phosphorous comnot limited to a hydrocarbon group such as the hydropounds of our invention can be any of the conventional carbon groups set forth above for R, or a halide group catalysts used in preparing phosphate esters. Examples such as chlorine or bromine; or NO or SR; or of suitable catalysts are metals such as copper powder, OR"; or COOR"'; or NR'R"; or iron filings, calcium, aluminum and magnesium; halides -NHR"NH or NHOH; NHR""OH; wherein such as aluminum chloride, magnesium'chloride, ferric R' is H or a hydrocarbon group as defined above for chloride, tin tetrachloride, zinc chloride, boron trifluo- R, and R"" is an alkylene group of 1-22 carbon atoms ride, titanium trichloride, and titanium tetrachloride; and preferably of l-l2 carbon atoms. Some specific 7 sulfates such as copper sulfate; and oxides such as mag- SR"'groups are -SH; -SCH SC H SC H nesium oxide and copper oxide. The preferred catalyst SC H and SC H Some specific OR"' groups is magnesium. The amount of catalyst is usually present are -OH, OC H OCGHH; -OCH OC H in amounts between 0.5 and 5 percent based on the and OC H weight of phenolic compounds.

Some specific COOR groups are COOl-l; The diluent can be any liquid, provided itis inert (not COOC H COOC H COOC H reactive in any manner which will harm the reaction or COOC H and COQCH V V H V WWW 40 the product) and should dissolve at least one of the resome specific m groups are NH2; actants. Examples of suitable solvents are the chlorinated hydrocarbons. The preferred solvent is O- dichlorobenzene. The quantity of diluent is most com- "NHCHZF i i i monly present in amounts between 50 and 300 percent COHB a s am by weight of the phenolic compounds.

' H The process is not limited to specific reaction tem- NHCH"; N(CH")fi N(CH)2; and peratures, since the reaction can be carried out over a CH wide range of temperatures. For examples, the process r e we l.- can be carried'out at temperatures of from about 0C.

Some specific -NHR""NH groups are to temperatures of about 200C. The preferred temper- -NHCH NH -NHC H NH NHC H NH and ature range varies from about 150C to 200C., and the NHC H, NH most preferred temperature range is from about 165C.

Some specific NHR""OH groups are NHC- to 175C. Also the process is not limited to any specific H OH; NHC H OH; NHC H OH; and NHC H- reaction time, since the time required will vary, primar- ,OH, ily dependent upon the particular reactants, tempera- R" preferably is an alkyl group containing at least tures, and catalysts. Preferably the reaction times vary one carbon atom with methyl being the most preferred. from about 12 to about 72 hours. About 24 hours is the Usually alkyl groups of not more than 22 carbon atoms reaction time which ismost commonly used. are employed; advantageously the alkyl group contains Atmospheric pressure is the most commonly used l-l2 carbon atoms. pressure for carrying out our invention. Of course,

Specific examples of suitable bisphenols are 4,4- higher or lower pressures can be employed when demethylenebis-(2,6-dimethylphenol); 2,2- sired. methylenebis-(4-ethyl-6-tert.-butylphenol), 2,2'- Some of the novel phosphate esters of our invention @E lY t ll9K913i???-' Ph(l9lL,.. 2122. 25?, 9s !a sdhxthefqflqwins strustures wherein R,R',.and R" and n have the same definitions and positions set forth in respect to Formula I. A

The phosphorous compounds of the invention are useful as antioxidants in a wide variety of materials. Among such materials are synthetic polymers rubber, waxes, fats, and oils. Among the synthetic polymers which can be stabilized with the products of this inven- 7 tion are: polyolefinssuch as polyethylene, polypropylproportions dependent upon the identity of the specific polymeric material, the desired degree of stabilization, and the environment in which the material is to be used. An amount of about 0.1 percent by weight based upon the material to be stabilized is very effective. The threshold at which the compounds of the invention are effective is about 0.001 percent by weight based upon the weight of material to be stabilized. The compounds of the invention are used in amounts as high as 5 percent by weight or higher based upon the weight of ma- EXAMPLE 1 To a mixture of 3 moles of 2,2'.-methylenebis-(4- methyl-6-tert. butylphenol) 3000 parts of odichlorobenzene, as an inert solvent, and 0.4 moles of a magnesium metal catalyst in a glass-lined container or flask equipped with a glass-surfaced-stirrer or agitator is added all at once and with agitation, 1 mole of phosphorous oxychloride. The resultant mixture is agitated for 24 hours at a pressure of about one atmosphere with the temperature being maintainedbetween 165 and 175C. Hydrogen chloride gas evolves as the reaction proceeds and is neutralized in a scrubbing device. The reaction mixture is cooled, 1,000 parts of water are added and the magnesium catalyst is separated by filtration. The'clarified mixture is then neutralized to a pH between 6 and 8 by use of an aqueous soldium carbonate solution and after washing with 1,000 parts of water the organic portion is then separated from the aqueous portion of the mixture. The reaction product and inert solvent are then separated by vacuum distillation. The reaction product, is a clear, friable glass melting between 65 and C, and has the following structure as determined by elemental analysis, and IR spectra:

CHa CH5 I a tris methyl-6-t-butylphenyl] Phosphate EXAMPLE 2 To a mixture of 2 moles of 2-tert.-butyl-4- methylphenol, 1 mole of 2,2'-methylenebis-(4-methyl- 6-tert.-butylphenol), 3000 parts of o-dichlorobenzene,

, as an inert solvent, and 0.4 moles of a magnesium metal satalyst in? ass-lined q ta us 9r flasksq i ps with a glass-surfaced stirrer or agitator is added all at once and with agitation, 1 mole of phosphorous oxychloride. The resultant mixture is agitated for 24 hours at a pressure of about one atmosphere with the temperature being maintained between and C. Hydrogen chloride gas evolves as the reaction proceeds and is neutralized in a scrubbing device-The reaction mixture is cooled, 1,000 parts of water are added and the magnesium catalyst is separated by filtration. The

clarified mixture is then neutralized to a pH between 6 and 8 by use of an aqueous sodium carbonate solution. The organic portion of the mixture is then washed with 1000 parts of water, and an organic layer is then separated from the aqueous portion of the mixture. The reaction product and inert solvent are then separated by vacuum distillation. The reaction product, di[ (2-tert.-

[2-(2-hydroxy-3-t-butyl-5-methylbenzyl)-4- H I C(CHah 2 2 l)a I30 206' CH, CH;

EXAMPLE 3 To a mixture of 3 moles of 2,2'-methylenebis-6-tert.- butyl-4-chlorophenol), 3000 parts of odiclorobenzene, as an inert solvent, and 0.4 moles ofa' magnesium metal catalyst in a glass-lined container or flask equipped with a glass-surfaced stirrer or agitator is added all at once and with agitation, 1 mole ofphosphorous oxychloride. The resultant mixture is agitated for 24 hours at a pressure of about one atmosphere with the temperature being maintained between 165 and 175C. Hydrogen chloride gas evolves as the reaction proceeds and is neutralized in a scrubbing device. The reaction mixture is cooled, 1000 parts of water are added and the magnesium catalyst is separated by filtration. The clarified mixture is then neutralized to a pH between 6 and 8 by use of an aqueous sodium carbonate solution. The organic portion of the mixture is then washed with 1,000 parts ofwater, and an organic layer is then separated from the aqueous portion of the mixture. The reaction product and inert solvent are then separated by vacuum distillation. The reaction product, trisl 2-(2-hydroxy-3-tert.-butyl-5- chlorobenzyl)-4-chloro-6-tert.-butylphenyl] phosphate, has the following structure as determined by element ana y an 1B P P r HO 1 P=O C(CHz)a r 1 V t 51 EXAMPLE 4 To a mixture of 3 moles of 4,4'-methylenebis-2,6- ditert.-butylphenol, 3,000 parts of o-dichlorobenzene as an inert solvent, and 0.4 moles of a magnesium metal catalyst in a glass-lined container or flask equipped with a glass-surfaced stirrer or agitator is added all at once and with agitation, 1 mole of phosphorous oxychloride. The resultant mixture is agitated for 24 hours at a pressure of about one atmosphere with the temperature being maintained between 165 and 175C. Hydrogen chloride gas evolves as the reaction proceeds and is neutralized in a scrubbing device. The reaction mixture is cooled, 1000 parts of water are added and the magnesium catalyst is separated by filtration.,The clarified mixture is then neutralized to a pH between 6 and 8 by use of an aqueous sodium carbonate solution. The organic portion of the mixture is then washed with table below:

l 1000 parts of water, and an organic layer is then separated from the aqueous portion of the mixture. The reaction product and inert solvent are then separated by vacuum distillation. The reaction product, tris [4-(4- hydroxy-3,5-ditert.-butylbenzyl)-2,6-ditert.-

butylphenyl] phosphate, has the following structure as dete m nes by. el me a ana ys s 99.113 .spest aa.

EXAMPLE A The product of Example 1 is admixed with a polyethylene of 0.960 density and approximately 300,000 molecular weight in a steel container and the mixture is extruded twice at 300F. The concentration of the product of Example 1 is then adjusted to 0.1 percent by weight of the polymer by the addition of more of the polyethylene and the mixture is again extruded twice at 300F. The resulting polyethylene composition is then pressed into a 6 6.5 mil film at 310F. and 1,280 p.s.i. on a 10 inch hydraulic ram press. Likewise a film of the same polyethylene without any antioxidant and a film of the same polyethylene containing 0.1 percent by weight of some other antioxidants are prepared by the method set forth above. The resulting films are then subjected to i 1C. in a forced draft oven. The absorbance in the carbonyl region of the 1R Spectrum (5.8 Angstroms) is then recorded after periods of exposure. When the observed absorbance reaches 94 percent, the sample is consisered to be oxidized" and the time of exposure to reach this point is recorded in the TABLE 1 Time in hrs. to

reach 94% absorbance Additive Amount ahf] Reaction Product of Example 2. Reaction Product of Example 3.

EXAMPLE B lecular weight in a steel container and the mixture is ex truded twice at 380F. The resulting polypropylene compositions containing 0.5 percent by weight, of the product of Example 1 are then pressed into a 6 6.5 mil film at 350F. and 1280 psi. on a 10 inch hydraulic ram press. Likewise a film of the same polypropylene without any antioxidant and a film of the same polypropylene containing 0.5 percent of 2,2-methylenebis-(6- t-butyl-4-methylphenol) are prepared by the method set forth above. The resulting three films are then subjected to 150 1C. in a forced draft oven. The absorbance in the carbonyl region of the IR Spectrum (5.8 microns) is then recorded after periods of exposure. When absorbance reaches 94 percent the sample is considered to be oxidized, and the time of exposure to reach this point is recorded in the table below:

TABLE II Time in hrs. to reach 94% Additive Amount Absorbances NONE 4 2,2'-methylenebis-(6'tbutyl-4-methylphenol) 0.5

Reaction Product of Example I 0.5 I39 6-t-butylphenyl] phosphate.

10 What isclaimed is: 1;. A phosphate ester of the formula:

wherein n is l or 2, R is independently selected from saturated aliphatic hydrocarbon linkages (i.e. alkylidenes and alkylenes) of l 8 carbon atoms, wherein R is independently selected from alkyls of l 12 carbon atoms, R" is independently selected from alkyls of l 12 carbon atoms with the provision that the hydroxyl group on one ring and the oxygen residue of same after removal of hydrogen on the other ring is ortho or para to R, that all ortho and para positions to said hydroxyl and oxygen residue are substituted, that one bisphenol moiety can be attached to the phosphorous atom through both hydroxyls by removal of hydrogen to form a ringed substituent.

2. A phosphate ester according to claim 1 wherein R is methylene.

3. A phosphate ester according to claim 2 wherein the hydroxyls on each ring are ortho to R.

4. A phosphate ester according to claim 3 wherein R is a tertiary'butyl radical.

5. The phosphate ester according to claim 1 which is tris [2-( 2-hydroxy-3-t-butyl-5-methylbenzyl)-4-methyl- UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,812 Dated May 21 1 974 Inventor(s) Michael Robin and Sheldon R Schulte It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In Column 3, llne 43; "NH NI-ICH -N(CH -N should be corrected to --N(CH -N In Column 8, line 13; "4" should be corrected to 3.

Signed and sealed this 17th day of September 1974.

(SEAL) Attest:

C. MARSHALL DANN MCCOY M. GIBSON JR. Attesting Officer Commissioner of Patents LJSCOMM-DC 60376-06) u cnvzmmnu mzmnuc. orrltr. 1969!)166-334 UNITED S'IATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,812,220 Dated May 21 197 4 lnventor(s) Michael Robin and Sheldon R Schulte It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

' (1 1-1 In Column 3, line 43; "NH -NHCH -N(CH -N should be corrected to In Column 8, line 13; "4" should be corrected to 3-.

Signed and sealed this 17th day of September 1974.

(SEAL) Attest: McCOY M. GIBSON JR. C. MARSHALL DANN Commissioner of Patents Attesting Officer USCOMM-DC 6037641169 

2. A phosphate ester according to claim 1 wherein R is methylene.
 3. A phosphate ester according to claim 2 wherein the hydroxyls on each ring are ortho to R.
 4. A phosphate ester according to claim 3 wherein R'' is a tertiary butyl radical.
 5. The phosphate ester according to claim 1 which is tris (2-(2-hydroxy-3-t-butyl-5-methylbenzyl)-4-methyl-6-t-butylphenyl) phosphate. 